NHLBI convened a workshop to discuss opportunities and needs for implementation science research in critical care. Critical illness is an important public health problem. There are more than 5 million intensive care unit admissions each year in the United States. Morbidity, mortality, and costs associated with critical illness are extremely high, with mortality for critical illness syndromes such as acute respiratory distress syndrome and severe sepsis of up to 50%. NHLBI has a strong interest in critical care research for heart, lung, and blood diseases and a long history of supporting basic and clinical critical care research including efficacy studies.